Below is an answer from 2010. Not sure if something has changed since then...
DFSORT can use zIIP on behalf of DB2 utiltiies, but not otherwise. Here's more information:
At this time, IBM has no plan for enabling DFSORT to exploit the IBM System z Integrated Information Processor (zIIP). IBM realizes DFSORT remains a prominent component of our customers' batch workloads; however, current testing, prototypes and data analysis indicate the value may be marginal for the majority of our customers. IBM will continue to focus its DFSORT development efforts on the enhanced function, performance, reliability and service items that we believe provide the most value to our clients.
DB2 Utilities Suite for z/OS uses a small set of DFSORT sort function. Worldwide, there has been a tremendous increase in DB2 for z/OS activity (due to such things as database consolidations, remote connectivity, business intelligence, and specialty engine exploitation). This increase in DB2 activity has led to an increase in database maintenance workloads which often drive bursts of parallel utility processing during scheduled maintenance windows. As a result, additional offload by DB2 Utilities Suite for z/OS is supported.